//跳台阶扩展问题
import java.util.Scanner;

注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
   public static void main(String[] args) {
       Scanner in = new Scanner(System.in);
       int n = in.nextInt();
       int[] arr = new int[20];
       arr[0] = 1;
       arr[1] = 2;
       arr[2] = 4;
       for (int i = 3; i  n; i++) {
           int sum = 0;
           for (int j = 0; j  i; j++) {
               sum += arr[j];
           }
           arr[i] = sum+1;
       }
       System.out.println(arr[n-1]);
   }
}